Machines, including wheel loaders, on and off-highway haul and vocational trucks, motor graders, and other types of heavy equipment generally include a mechanical transmission drivingly coupled to opposing traction devices by way of front and/or rear differentials and two substantially identical final drives (one located between each differential and an associated traction device). Each differential receives a power input from the transmission and produces two power outputs directed through the final drives to the traction devices. The final drives function to reduce a rotational speed of the differential output to a level appropriate to drive the associated traction devices and thereby propel the machine.
Each final drive generally includes a stationary housing, an axle rotatably disposed within the housing and driven by the differential, and a brake assembly connected between the housing and the axle. Typical brake assemblies include a plurality of friction plates connected to rotate with the axle, a plurality of separator plates disposed between adjacent friction plates and rotationally constrained at their periphery by the housing, and a piston configured to push the friction plates and separator plates together, thereby generating frictional torque between the plates that retards rotation of the axle. Brake assemblies that are cooled via fluid are known as wet brake assemblies. Brake assemblies that are cooled via circulating fluid are known as force-cooled wet brake assemblies.
An example of a wet brake assembly is described in U.S. Pat. No. 4,655,326 issued to Osenbaugh on Apr. 7, 1987 (“the '326 patent”). Specifically, the '326 patent discloses a multiple disc brake that is located at a planetary wheel end of a final drive. The brake includes a plurality of rotatable and non-rotatable discs disposed within a stack for selectively interconnecting ring and sun gears of a planetary drive unit. The brake also includes a piston for engaging and moving the disc stack into frictional contact with a carrier of the planetary drive unit to restrain rotation of the sun gear and an output member. The piston is contained within a chamber formed by a portion of the planetary drive unit ring gear and a portion of an adapter secured to the outer end of a non-rotatable spindle. An oil circulation system is incorporated into the outer end of the spindle to supply oil to an inner periphery of the disc stack, allowing the oil to flow radially outward through the disc stack, thereby cooling the brake.
The brake of the '326 patent may be less than optimal. In particular, because the cooling oil is supplied to the inner periphery of the disc stack, restrictions associated with flow through the disk stack could raise a pressure of the oil at locations upstream of the disc stack. In some situations, this elevated pressure could cause seals that are located upstream of the disc stack (e.g., between the spindle and the ring gear) to leak.
The brake assembly of the present disclosure is directed toward solving one or more of the problems set forth above and/or other problems of the prior art.